ACTION OF INTESTINAL BACTERIA ON PROTEIDS. 467 
(b) Substances formed directly and not from tyrosine — indol, skatol, and 
skatolcarbonic acid. 
Of these substances, Zumft 1 found indol, skatol, phenol, and para- 
kresol in the large intestine of man, but skatolcarbonic acid was absent; 
this latter acid has not yet been detected in the intestine. According 
to E. Salkowski, it is excreted unchanged in the urine, and he states that 
he has detected it in normal urine. 2 
These, several substances may now be considered seriatim. 
Derivatives of tyrosine formed in -putrefaction. 3 — Hydroparacumaric acid, 
or paraoxyphenylpropionic acid (HO.C 6 H 4 .C 2 H 4 .COOH) crystallises from 
water in anhydrous monoclinic crystals, melting at 1 25 —128 J C, soluble 
in water, alcohol, and ether. It gives a transient blue coloration with ferric 
chloride, and a red coloration or red precipitate when boiled with Millon's 
reagent. It is the oxy-aeid of phenylpropionic arid, which has also been 
found among the putrefaction-products of proteids. Phenylpropionic acid 
crystallises in slender needles, melting at 47°-48° C. (B-Pt. 280° C). As 
follows from its constitution, its solutions do not give Millon's reaction. 
Paraoxyphenylacetic acid (HO.C 6 H 4 .CH 2 .COOH) crystallises from water 
in prismatic crystals, melting at 148° C., and soluble in water, alcohol, and 
ether. "With ferric chloride it gives a faint violet coloration, changing to 
a dirty grey -green. It also gives Millon's reaction. Phenylacetic acid 
crystallises in scales, which melt at 76° "5 C. 
Phenol and parakresol* are also formed in the bacterial decomposition of 
tyrosine ; they are absorbed from the alimentary canal, and after conversion 
into ethereal sulphates are excreted in the urine. The amount of these 
ethereal sulphates in the urine gives a measure of the amount of bacterial 
decomposition going on in the intestine. 5 
Tyrosine and its derivatives are very closely related to one another. In 
the derivation of these compounds, according to Baumann, 6 tyrosine (paraoxy- 
phenyl-a-amiclopropionic acid) undergoes reduction, ammonia being split off, 
and hydroparacumaric acid (paraoxyphenylpropionic acid) formed. This 
compound, by a series of oxidations, accompanied by a splitting off of carbon- 
dioxide, yields paraoxyphenylacetic acid and parakresol. Parakresol is said 
to similarly yield phenol. 
These changes are illustrated by the following equations : — 
OH (p) .OH ( P ) 
c g h/ + h 2 =c 6 h/ +NH 3 
x CH,.CH(XH 2 ).COOH x CH 2 .CH,.COOH 
(paraoxyphenyl-a-amidopropionic (paraoxyphenylpropionic acid 
acid or tyrosine) or hydroparacumaric acid) 
/OH ( P ) /OH (p) 
2C H / + 30., = 2C,jH/ + 2C0 2 + 2H o 
x CH,.CH ? .COOH x CH 2 .COOH 
(paraoxyphenylpropionic acid) (paraoxyphenylacetic acid) 
1 Arch. d. sc. bloL, St. Petersbourg, 1892, vol. i. p. 497. 
3 Ztschr. f. physiol. Chcm., Strasslmrg, 1885, Bd. ix. S. 32. 
3 See Baumann. Ztschr. f. physiol. Chcm,, Strassburg, 1877-1880, Bd. i. S. 60 ; iv. S. 304 ; 
Ber. d. deutsch. chem. Gesellsch., Berlin, 1879, Bd. xii. S. 1450; 1880, Bd. xiii. S. 279; 
Baumann and Brieger, Ztschr. f. -physiol. Chcm., Strassburg, 1879, Bd. iii. S. 149 ; E. 
and H. Salkowski, Bcr. d. deutsch. chcm. Gesellsch., Berlin, 1879, Bd. xii. S. 648 ; E. 
Salkowski, Ztschr. f. -physiol. Chem., Strassburg, 1878-9, Bd. ii. S. 420 ; AVeyl, Hid., 
1877-9, Bd. i. S. 339 ; iii. S. 312. 
4 For a description of the physical and chemical properties of these bodies, see 
Gamgee, " Physiological Chemistry of the Animal Body," 1893, vol. ii. p. 434. 
5 Baumann, Ztschr. f. 'physiol. Chem., Strassburg, 1886, Bd. x. S. 123. 
6 Ber. d. deutsch. chcm.' Gesellsch., Berlin, 1879, Bd. xii. S. 1450. 
